Conventionally, vertical filling-packaging machines have been used to package liquid or pasty fillers in bags (for example, see JP-Application No.-93-319708 which is JP Laid-open No. H07-172403).
FIG. 1 is a diagram illustrating an example of conventional vertical filling-packaging machines, which is shown in the foregoing document.
Vertical filling-packaging machine 101 forms a sheet-type film 161 into a cylindrical shape using back forming guide 105, and thermally seals matching surfaces of the cylindrical film using vertically sealing mechanism 106. Then, a filler is introduced into thus formed cylindrical film 160 to manufacture a packaging bag.
Vertical filling-packaging machine 101 comprises film feeding rollers 107 for carrying cylindrical film 160 downward; introduction nozzle 108 for introducing a filler into cylindrical film 160; a pair of ironing rollers 125 for squeezing cylindrical film 160 into a flat shape to form flat part 160a; transverse sealing mechanism 130 for thermally sealing flat part 160a in a width direction of cylindrical film 160; and cutting mechanism 140 which contains cutter 141 for cutting the transversely sealed part which has been thermally sealed by transverse sealing mechanism 130. The distance between transverse sealing mechanism 130 and cutting device 140 in a direction in which cylindrical film 160 is carried (vertical direction as shown in FIG. 1) is set to correspond to the length of one packaging bag to be manufactured. In this connection, the thermal sealing operation by thermal sealing mechanism 130 is also called “transverse sealing.”
Exemplary operations of vertical filling-packaging machine 101 configured in this way will be described with reference to FIG. 2.
In a state illustrated in FIG. 2A, a pair of ironing rollers 125, transverse sealing mechanism 130, and cutting mechanism 140 remain in an open state. Also, one packaging bag 166 has already been formed below cylindrical film 160. A filler is being continuously introduced into cylindrical film 160 from introduction nozzle 108 (see FIG. 1).
Next, as illustrated in FIG. 2B, as the level of the filler exceeds the position of ironing rollers 125, cylindrical film 160 is nipped by ironing rollers 125 to divide the filler.
Next, as illustrated in FIG. 2C, ironing rollers 125 are driven to rotate with cylindrical film 160 remaining nipped, thereby carrying cylindrical film 160 downward while forming flat part 160a in cylindrical film 160. This carrying operation is continued until transversely sealed part 165, which has been thermally sealed in the previous step, reaches a position at which it is sandwiched by cutting mechanism 140.
Next, as illustrated in FIG. 2D, transverse sealing mechanism 130 and cutting mechanism 140 are driven while the carriage of cylindrical film 160 is stopped. Transversely sealing mechanism 130 nips flat part 160a formed by a pair of ironing rollers 125 to form transversely sealed part 165 in the width direction of cylindrical film 160. Cutting mechanism 140, in turn, nips transversely sealed part 165 thermally sealed in the previous step to cool transversely sealed part 165 in which heat still remains, and advances cutter 141 to cut transversely sealed part 165 in the width direction. In this way, packaging bag 166 is cut off from cylindrical film 160.
Next, as illustrated in FIG. 2E, a pair of ironing rollers 125, transverse sealing mechanism 130 and cutting mechanism 140 are all brought into an open state. By opening cutting mechanism 140, the holding state by cutting mechanism 140 is released to provide one packing bag 166.
Then, film feeding rollers 107 (see FIG. 1) are driven to again carry cylindrical film 160 until the state shown in FIG. 2A appears. By repeating a series of steps as described above, packing bags 166 filled with the filler are manufactured in sequence.
After forming transversely sealed part 165 in cylindrical film 160 using transverse sealing mechanism 130 in this way, vertical filling-packing machine 101 of FIG. 1 again carries cylindrical film 160 downward, and cools and cuts transversely sealed part 165 by using cutting mechanism 140.
Japanese Patent No. 2598879, for example, has proposed a mechanism which is capable of fully performing operations for thermally sealing, cooling and cutting cylindrical film 160 while the carriage of the film is stopped.
FIG. 3 is a diagram for describing the configuration and operation of a conventional sealing and cuffing mechanism proposed in Japanese Patent No. 2598879.
As illustrated, transverse sealing and cutting mechanism 230 comprises heater bar 201 and heater bar receiver 204 for thermally sealing flat part 160a of a cylindrical film in its width direction, and comprises cooling bar 202 and cutting device 205 for cooling and cutting a transversely sealed part that is thermally sealed by heater bar 201 and heater bar receiver 204.
Heater bar 21 and cutting device 205 are driven by a power source, for example, an air cylinder, and are configured to advance and retract in directions perpendicular to flat part 160a. Cooling bar 202 and heater bar receiver 204 in turn are pivotably supported by supporting shafts 210a, 210b, respectively, and are configured to pivotally move about supporting shafts 210a, 210b in step with advancing and retracting movements of heater bar 201 and cutting device 205, specifically, when cooling bar 202 is not in contact with flat part 160a, as illustrated in FIG. 3A, when heater bar 201 is advanced, and is in contact with flat part 160a, as illustrated in FIG. 3B and when heater bar 201 is retracted. Heater bar receiver 204 in turn is in contact with flat part 160a, as illustrated in FIG. 3A, when cuffing device 205 is retracted, and is not in contact with flat part 160a, as illustrated in FIG. 3B, when cutting device 205 is advanced.
Transversely sealing and cutting mechanism 230 configured as described above advances heater bar 201 and retracts cutting device 205, as illustrated in FIG. 3A, to apply pressure and heat to flat part 160a by using heater bar 201 and heater bar receiver 204, thereby thermally sealing flat part 160a to form a transversely sealed part. Subsequently, as illustrated in FIG. 3B, heater bar 201 is retracted, and cutting device 205 is advanced to sandwich flat part 160a between cutting device 205 and cooling bar 202 to cool the transversely sealed part in which heat still remains. After this cooling operation has been performed for a predetermined time, cutter 203 provided in cutting device 205 is advanced to cut the cooled transversely sealed part.
A vertical filling-packaging machine that uses such transverse sealing and cutting mechanism 230 to manufacture packaging bags provides the following advantages, since the thermal sealing, cooling, and cutting operations can be fully carried out while the cylindrical film is stopped.
Vertical filling-packaging machine 101 shown in FIG. 1, after performing a thermal sealing operation, again carries the cylindrical film downward until transversely sealed part 165 formed thereby reaches the height of cutting mechanism 140. Therefore, a large sealing width must be used in consideration of variations in the amount of fed cylindrical film. However, when transverse sealing and cutting mechanism 230 is used, the sealing width can be reduced because such variations need not be taken into consideration. A large sealing width means that extra cylindrical film is used, leading to an increase in the manufacturing cost of packing bags as products. Next, since transverse sealing and cutting mechanism 230 need not carry the cylindrical film downward as described above, and can therefore reduce the time required for thermal sealing, cooling, and cutting operations, the packing bag manufacturing operation can therefore be performed at higher speeds
Other exemplary operations of vertical filling-packing machine 101 will be described with reference to FIG. 4.
First, as illustrated in FIG. 4A, a filler from introduction nozzle 108 is filled into cylindrical film 160, the lower end of which is thermally sealed. As illustrated, the lower end of cylindrical film 160 is at a position at which a packaging bag manufactured in the preceding manufacturing step was cut off, and is at the same height as the cuffing edge of cutter 141. Also, area A, which is to be thermally sealed in a transverse sealing step, later described, is positioned above ironing rollers 125.
Next, as illustrated in FIG. 4B, cylindrical film 160 is carried downward until the level of the filler falls below ironing rollers 125.
Next, as illustrated in FIG. 4C, cylindrical film 160 is nipped by a pair of ironing rollers 125 in an area above the level of the filler, and ironing roller 125 are driven to rotate. Consequently, the cylindrical film is carried downward while flat part 160a is formed. This carrying operation is performed until area A, which is to be thermally sealed, reaches the height of transverse sealing mechanism 130.
Subsequently, cylindrical film 160 is thermally sealed in its width direction using thermal sealing mechanism 130, cylindrical film 160 is again carried downward, and cylindrical film 160 is cut by using cutting mechanism 140, thereby manufacturing one packaging bag.